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Date: Tue, 10 Dec 1996 21:17:26 -0800 (PST)
From: John Dyson <dyson>
Message-Id: <199612110517.VAA14335@freefall.freebsd.org>
To: CVS-committers, cvs-all, cvs-sys
Subject: cvs commit:  src/sys/ufs/ufs ufs_readwrite.c
Sender: owner-cvs-sys@FreeBSD.ORG
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dyson       96/12/10 21:17:25

  Modified:    sys/ufs/ufs  ufs_readwrite.c
  Log:
  Significant performance improvement for mmap'ed files.  This commit
  makes MADV_SEQUENTIAL much more effective.  I suggest that
  we start using MADV_SEQUENTIAL on system utilities that mmap
  their input files, and the I/O is predominantely sequential.
  Below is a test with 'cmp' on two relatively large binary files,
  where the files are so large that the caching is ineffective:
  
  + ls -l t1.xxx t2.xxx
  -rw-r--r--  1 root  wheel  65598384 Dec 10 12:13 t1.xxx
  -rw-r--r--  1 root  wheel  65598384 Dec 10 12:14 t2.xxx
  
  + time cmp t1.xxx t2.xxx
  3.78user 0.70system 1:33.43elapsed 4%CPU
  
  + time cmpmadv t1.xxx t2.xxx
  4.21user 1.05system 0:30.93elapsed 17%CPU
  
  This change is as a result of an observation made by BDE.
  
  Revision  Changes    Path
  1.23      +41 -1     src/sys/ufs/ufs/ufs_readwrite.c